Tapchanging voltage regulators providing a regulating range of +/−10% are used on single and three phase power distribution lines. Some electric power distributions substations use sets of three regulators on three phase distribution lines as they leave the substation. Usually each regulator is supplied by a single phase transformer for reducing the voltage from that of the substation primary feed to the voltage of the regulator. Regulators so applied are referred to as “station regulators”.
Other substations supply voltage reduced by a single three phase transformer feeding lines from a distribution substations to users of electric power. Such transformers have taps on the winding switched by a tapchanging switch. Control devices for such switches are known as Load Tapchanging (LTC) Controls. Such devices control all three phase voltages based on sensing but one of the three phases.
In either instance line regulators are used along single and three phase distribution lines which extend from distribution substations for re-regulating the voltage where required. Regulators are often referred to as “station” or “line” regulators depending on their location even though they may be identical in construction.
Regulators are also used in large industrial complexes to regulate voltages to compensate for varying processing loads. To reduce the fire hazard of oil filled regulators there is a need for dry type regulators to regulate voltages in very tall buildings.
Prior art regulators generally use an autotransformer with 16 steps for raising and 16 steps for lowering the voltage by up to 10%. The steps are changed by a motor driven tapswitch. The 16 steps are derived from eight transformer taps using a bridging autotransformer to form a voltage step midway between each pair of autotransformer taps.
For economy of autotransformer construction, prior art regulators often use a single eight tap winding that is reversed so as to either raise or lower voltages by a combination tapchanging and winding reversal switch. Improvements in cost realized from polarity reversal may be partially offset by increased switch cost of the switch and the need for a larger switch drive motor. In the construction of either LTC transformers or regulators the transformer and switch are housed in a tank filled with oil.
To enable changing a regulator for maintenance without shutting off power, it is necessary to place the regulator in neutral and bypass the regulator. The bypass is accomplished by a lineman either using a temporary jumper cable or by operating a permanently mounted by pass switch operated by an insulated hook switch. Tanks have been known to explode with deadly results when a bypass cable was installed when the regulator was not truly on neutral and the lineman was not in a safe location.
This prior art material together with non-inventive FIGS. 1, 2 and 3 are included for reference only to describe presently accepted practice. FIGS. 1, 2 and 3 are useful in describing the inventive regulator in its departure from prior art practice.
FIG. 1, labeled prior art, shows an outline of a General Electric Type VR-1™ regulator which uses a Beckwith Electric M-2001 control branded for General Electric. Note in particular the prior art voltage step indicator with drag hand reset. These indicate the present position of the regulator step position together with the maximum and minimum step position since the last time the drag hands were reset manually. The source and load connection terminals are shown together with a neutral terminal. While the neutral terminal is often connected to ground when installed there are instances where it is not. The control box is shown mounted on the regulator. Line regulators are typically mounted at power line height on platforms constructed between two poles. The controls may be mounted at ground level for ease of access without use of a bucket truck.
FIG. 2, labeled prior art, show the front panel of a Beckwith Electric model M-2001 control, marked for GE, as seen with the control box door open. The control marked GE-2011 has a display at the top. Pushbuttons marked U for up and D for down move items on the display. When a desired item is displayed it may be entered by pressing the pushbutton marked E.
An RS232 “COM2” port is shown for connecting a computer with a user interface program for such things as entering setpoints and obtaining historic and present data.
LEDs light to indicate the tapchanger motor operating to “RAISE” the tap position and another to indicate operation to “LOWER” the tap position. Power may flow in reverse through the regulator to nearby loads from a power feed at the end of a distribution line. When this happens the “REV PWR” LED lights. An “OK” LED lights when power is on and the control is operating properly as determined by self checking features of the control.
In FIG. 2 five panels to the right are as follows:    1. Panel 1 has three fuses. The first fuse labeled “TEST TERMINAL” is for the meter out banana jack terminals. The second fuse labeled “VOLTAGE” is for the voltage out banana jack terminals. The third fuse labeled “MOTOR POWER” for the motor power banana jack terminals. The banana jack terminals are all shown in the second panel.    2. Panel 2 has three sets of banana jack terminals: “VOLTAGE IN”, “MOTOR PWR IN” and “METER OUT” terminals which are used for testing the regulator either in the shop or after installation.    3. Panel 3 has a spring return switch at the left that is normally off but can be moved up to raise the tapchange switch a tap and down to lower the tapchange switch a tap. A non-spring return switch is used to place the control in automatic operation, to turn it off, or to place it in manual operation by means of the test terminals of the second panel.    4. Panel 4 has a switch to change from automatic operation to manual operation using the second panel.    5. Panel 5 has a drag hand reset pushbutton and a neutral light.
FIG. 3 marked Prior Art is a circuit diagram of a regulator manufactured by the Cooper Power Systems Division of Cooper Industries. In this instance the series winding has eight taps used either for raising or lowering the voltage as determined by the position of the reversing switch. The number of voltage steps is doubled to 16 raise or lower by use of the bridging reactor having an equalizing winding. Note that the switch operates at the high load/source voltage. The current transformer and control winding are insulated so as to permit the control to operate at ground potential. Note that the source, load and source/load bushings allow the regulator to operate without a local load carrying earth ground.